Bushell's Case, 24 Eng. Rep. 1006 (C.P. 1670), established that jurors may not be fined or imprisoned for returning a verdict that conflicts with the judge's assessment of the evidence. Chief Justice John Vaughan's opinion did not defend jury nullification - in fact, the opinion asserted that jurors must follow the judge's directions concerning the law - but the opinion has long been recognized as a crucial resource for those who advocate nullification. Modern defenses of jury nullification that draw on Bushell's Case often point to Vaughan's argument that jurors must be permitted to form their own views because reasonable people may disagree about a witness's credibility or the reliability of the evidence. In the 1680s, however, when Bushell's Case was first being publicly debated, commentators focused primarily on Vaughan's argument that because jurors were chosen from the locality where the crime occurred, they should be presumed to have personal knowledge of the facts of the case. By the late seventeenth century, however, this premise was untenable. This article considers why the "personal knowledge" argument might have been so appealing, despite its implausibility, and examines the process by which that justification for jury nullification gave way to the "independent assessment" argument. In the course of the movement from the first justification to the second one, Bushell's Case began to viewed as supporting the jury's right to find both fact and law - a right that Vaughan had never defended.